Method for preparing capacitive stress sensing intelligent fabric

ABSTRACT

A method for preparing a capacitive stress sensing intelligent fabric. Conductive yarn serves as an electrode of a capacitive sensor, and the conductive yarn is obtained by means of direct preparation, coating, doping, etc.; an insulating elastomer is coated on the conductive yarn as a dielectric material; and the conductive yarn, which has been subjected to insulation processing, is interlaced among common yarns by using interweaving and overlapping structures among fabric yarns. A fabric sensing array is formed by means of a common manufacturing technique, and the method can be widely applied to force monitoring, etc., for intelligent garments, intelligent homes, touch-control screens, electronic skin and three-dimensional fabric composite materials.

TECHNICAL FIELD

The disclosure relates to the field of textile fabrics, and more particularly to a method of preparing an intelligent fabric.

BACKGROUND

With the increasing demands of people on the quality of life, all aspects of life require more portable, more intelligent and more comfortable. Therefore, the concepts of “Internet of Things”, “Smart Home” and “Smart Clothing” are put forward, and the basis of realizing these concepts is to soften the sensing components. Stress sensor can obtain intuitive real-time stress data by converting mechanical signals into electrical signals and then transmitting the signals to a signal processor. Micro-stress induction can be used to detect biological signals, such as heartbeat, pulse and finger touch, which can also be applied to smart clothing, smart home touch control devices, medical biological signal monitoring and artificial skin of robots. Great-stress induction can be applied to sports gloves, socks, etc. to acquire the power point and strength of athletes for scientific and intelligent training.

Chinese Patent Publication No. CN106236015A discloses an intelligent mattress containing flexible fabric sensors. The sensing part of the mattress is prepared as follows: the fabric is placed in the liquid of the nano-pressure-sensitive functional material. The nano-pressure-sensitive functional material is penetrated into the interior of the fabric and embedded on the surface of the fabric by ultrasonic wave. Then the patterned electrodes and electrode leads are made on the flexible substrate by embossing, etching or printing to press or bond the electrode layer on the surface of the pressure-sensitive layer. The fabrication process of the sensing unit is complex, and the pressure-sensitive material is boned with the electrode layer, which is not easy to wash. Chinese Patent Publication No. CN106030467A discloses a sheet flexible sensor which is formed by depositing an electrode material on one side of a dielectric film. The flexible sensor can deform in different directions, including extending the touch sensor vertically, extending the touch sensor horizontally, compressing the touch sensor, bending the touch sensor, distorting the touch sensor or deforming the touch sensor in other ways. However, the sensor cannot be used to form fabric. Google's Project Jacquard comprises a sensor which is prepared by employing wires as electrodes, covering the wires with insulation coatings, and then wrapping them in ordinary yarns through jacquard weaving. The problem is that the finer wire is lack of ductility, difficult to weave and easy to break in the process of wearing, washing and folding.

SUMMARY

To overcome the defects of conventional intelligent fabric sensing units, such as complex structure, poor wearing comfort, and complex manufacturing process, there provided is a method of manufacturing a capacitive stress sensing intelligent fabric.

A method of manufacturing a capacitive stress sensing intelligent fabric comprises:

1) preparing conductive yarns from metal, carbon or conductive polymers by doping or coating;

2) coating an insulation polymer elastomer with dielectric properties on the surface of the conductive yarn obtained in 1), to yield electrode yarns integrating a dielectric material and the conductive yarns; and

3) weaving the electrode yarns obtained in 2) using traditional textile technology, to obtain a stress-sensing intelligent fabric.

Specifically, in 1), the conductive component of the conductive yarns is a metal, carbon, conductive polymer, or a mixture thereof; the preparation method of the conductive yarns comprises direct preparation, doping, coating or in-situ polymerization, or a combination thereof.

Specifically, in 2), the insulation polymer elastomer with dielectric properties is polydimethylsiloxane, styrene-butadiene-styrene, polyurethane, a derivative thereof, or a mixture thereof; the pressure sensitivity of the integrated electrode yarns can be regulated by adjusting the ratio of the elastomer prepolymer to the curing agent.

Specifically, in 3), the preparation mode of the stress-sensing intelligent fabric comprises weaving, knitting, three-dimensional plaiting, or a combination thereof.

Advantages of the method of preparing an intelligent fabric according to embodiments of the disclosure are summarized as follows.

The organic insulating elastomer is coated on the surface of the conductive yarn; the conductive yarn is used as the electrode and the insulating elastomer is used as the dielectric material. The sensitivity and measuring range of the capacitive sensor are controlled by controlling the elastic modulus of the elastomer. The fabric sensing array can be formed by using the conductive yarns with traditional manufacturing technology.

In view of the existing safety problems of capacitive sensors with metal wires interwoven in fabric, and metal wires are not resistant to bending, the disclosure provides a woven fabric sensing array based on an integrated yarn comprising dielectric material and conductive electrodes, which functions as warp and weft yarns spaced apart from ordinary yarns. The resolution of the sensing matrix is controlled by controlling the distance between the conductive yarn and the warp and weft yarns.

In view of the detection of biological signals such as pulse and heartbeat requiring the sensor to directly contact the human body, a close-fitting sensing array of knitted fabric is provided.

A three-dimensional fabric sensing array for engineering composite reinforcement is designed and applied to real-time monitoring of material stress and deformation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an integrated conductive yarn coated with an elastic rubber insulation layer.

FIG. 2 is a schematic diagram of a flexible sensor unit based on conductive yarns.

FIG. 3 is a schematic diagram of a plain woven fabric sensor array;

FIG. 4 is a schematic diagram of a weft knitted fabric sensor array; and

FIG. 5 is a schematic diagram of a three-dimensional fabric sensor array.

DETAILED DESCRIPTION

To further illustrate, embodiments detailing a method of manufacturing a capacitive stress sensing intelligent fabric are described below. It should be noted that the following embodiments are intended to describe and not to limit the disclosure.

A method of manufacturing a capacitive stress sensing intelligent fabric comprises coating an elastic dielectric material on a conductive yarn to form an insulating layer, integrating the electrode of a capacitive sensing unit and a dielectric layer into a yarn. Through the interlacing and overlapping of fabric yarns, the fabric sensor matrix comprising sensor array is woven by ordinary weaving technology, such as weaving, knitting and three-dimensional plaiting. The fabric sensor matrix is connected to a micro-signal processor to achieve various stress sensing functions.

Example 1

A method of preparing a yarn-like sensor integrating dielectric materials and electrodes and a woven fabric sensor array thereof is provided. The insulating elastomer is made of polydimethylsiloxane (PDMS), styrene-butadiene-styrene (SBS), or a mixture thereof. The elastic modulus of the elastomer can be controlled by controlling the ratio of prepolymer to its crosslinking agent. The range of modulus can be changed between 2 and 40 MPa, and the corresponding sensitivity range is 0.01-4 KPa⁻¹. The lower the modulus, the higher the sensitivity. When the sensitivity is higher than 0.5 KPa⁻¹, the sensor can be used to monitor the physiological state of human body such as heartbeat and pulse. Sensors below this sensitivity can be used for touch sensing in smart clothing and smart home.

The conductive yarn is made of metal, carbon, conductive polymer, or a mixture thereof by a direct method. In order to enhance the strength of the conductive yarn, the conductive yarn can be prepared by doping and coating conductive metals and carbon nanomaterials on high strength and high modulus yarns such as nylon and aramid.

Preparation of insulating elastomers: the ratio of PDMS prepolymer to crosslinking agents is 5:2, 10:1, 20:1, 30:1 and 40:1, respectively. The determination of the ratio depends on the sensitivity of the required sensor. The two ingredients are uniformly mixed at room temperature and vacuumized for half an hour to remove the bubbles.

Coating and drying of elastic insulator: the conductive yarn is repeatedly soaked and dried in the above viscous liquid after debubbling, and the thickness of the coating can be controlled according to the fineness requirements of the yarn in the subsequent manufacturing process. The obtained yarn structure is shown in FIG. 1.

A capacitive sensor is formed by interlacing the warps and wefts of two conductive yarns fabricated by the above method. The structure of the sensor is shown in FIG. 2.

A capacitive sensor array is formed by interweaving the conductive yarns as warps and wefts using traditional woven manufacturing technology, as shown in FIG. 3. In the example, the invention is illustrated with a plain weave as an example, but is not limited to plain weave.

Example 2

A method of preparing a conductive polymer based yarn-like or fibrous sensor integrating dielectric materials and electrodes and a woven fabric sensor array thereof is provided. To solve the problem that knitted fabric has high ductility, the yarn-like or fibrous sensor and a woven fabric sensor array thereof employs a conductive polymer as electrodes. Polyurethane (PU), polyhydrostyrene-polyethylene-butene-polystyrene block copolymer (SEBS), or a mixture thereof are used as insulating elastomers to prepare an integrated yarn-like or fibrous sensor by melt extrusion and direct coating applied to fabrics.

The conductive fibers or yarns are prepared by wet spinning with PEDOT: PSS (poly (3, 4-ethylenedioxythiophene): polystyrolsulfon acid) and a ductile conductive reinforcement (dodecyl benzene sulfonic acid, sodium dodecyl benzene sulfonic acid) or polyaniline (PAni) as raw materials. Take polyaniline as an example, 20 wt. % polyaniline is dissolved in dichloroacetic acid (DCA) and heated in a water bath to 70° C. to yield a spinning solution. Polyaniline conductive fibers are prepared by wet spinning and acetone as a coagulation bath. The conductive fibers are dried in a vacuum oven at 50-60° C.

Coating of elastic dielectric insulation material: the PDMS prepolymer and the crosslinking agent are mixed in a ratio the same as that in Example 1 to yield a viscose, or the PU is melted to yield a viscous flow polymer. The viscose, viscous flow polymer or a mixture thereof is coated on the conductive yarn, and dried to yield a uniform elastic insulating dielectric layer.

Formation of woven fabric sensor array: take weft plain stitch as an example but the disclosure is not limited in this. Two adjacent yarns adopt the conductive yarn, and the capacitive stress sensor is formed at the overlap of the settlement arc of the coils, as shown in FIG. 4. The conductive yarns made of PEDOT: PSS and PAni conductive polymers have good ductility and can adapt to the deformation of knitted fabrics. Knitted fabrics are mostly used in close-fitting clothing, such as underwear, swimsuit, elastic sportswear, etc., can monitor physiological signals such as pulse and heartbeat of human body, and can be used for training supervision of athletes and monitoring of patients' physical condition.

Example 3

A conductive yarn-based capacitive sensor and use thereof in preparation of reinforcement composite of three-dimensional fabrics. Three-dimensional fabrics, featuring varied three-dimensional structures and convenient processing, are often used as reinforcements of engineering composite materials. In this example, a conductive yarn is combined with an insulating resin to yield a capacitive sensor for real-time monitoring of deformation of engineering composite materials.

Preparation of conductive yarn: following the operations in Examples 1 and 2, a metal, carbon, conductive polymer, or a mixture thereof used as conductive agents to prepare a conductive yarn using a direct method. To enhance the strength of the conductive yarn, conductive metals and carbon nanomaterials are doped or coated on high strength and high modulus nylon and aramid yarns.

Formation of yarn type electrode and elastic dielectric material: one or more insulating elastomer materials in Examples 1 and 2, for example, the PU and PET composite is coated on the conductive yarn. The mechanical properties such as compressive modulus of elasticity, shear stiffness and bending stiffness of insulating dielectrics can be controlled by using different molecular weight of insulating elastomers or different composite ratios, to yield stress sensors with different sensitivity.

Formation of capacitive stress-strain sensor: the bottom and top yarns of three-dimensional fabrics adopt the aforesaid conductive yarn, and a certain length is reserved as a lead to connect an external detection circuit. The prepared three-dimensional fabrics are directly compounded with resins and other matrices, and cured through hot rolling to yield a three-dimensional fabric composite, to monitor the pressure and deformation of the material in real time, so as to judge whether the material in use needs to be repaired or replaced or not.

It will be obvious to those skilled in the art that changes and modifications may be made, and therefore, the aim in the appended claims is to cover all such changes and modifications. 

What is claimed is:
 1. A method of manufacturing a capacitive stress sensing intelligent fabric, the method comprising: 1) preparing conductive yarns from metal, carbon or conductive polymers by doping or coating; 2) coating an insulation polymer elastomer with dielectric properties on the surface of the conductive yarn obtained in 1), to yield electrode yarns integrating a dielectric material and the conductive yarns; and 3) weaving the electrode yarns obtained in 2) using traditional textile technology, to obtain a stress-sensing intelligent fabric.
 2. The method of claim 1, wherein in 1), a conductive component of the conductive yarns is a metal, carbon, conductive polymer, or a mixture thereof; the preparation method of the conductive yarns comprises direct preparation, doping, coating or in-situ polymerization, or a combination thereof.
 3. The method of claim 1, wherein in 1), a preparation method of the conductive yarns comprises direct preparation, doping, coating or in-situ polymerization, or a combination thereof.
 4. The method of claim 1, wherein in 2), the insulation polymer elastomer with dielectric properties is polydimethylsiloxane, styrene-butadiene-styrene, polyurethane, a derivative thereof, or a mixture thereof.
 5. The method of claim 1, wherein in 2), the pressure sensitivity of the integrated electrode yarns can be regulated by adjusting the ratio of the elastomer prepolymer to the curing agent
 6. The method of claim 1, wherein in 3), the preparation mode of the stress-sensing intelligent fabric comprises weaving, knitting, three-dimensional plaiting, or a combination thereof. 